Browsing by Author "Selcuk, Ahmet"

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Determination of the Optimum Conditions for Boric Acid Extraction From Ulexite in Perchloric Acid Solutions
(Asian Journal of Chemistry, 2008) Gur, Aycan; Yildiz, Adnan; Celik, Hilal; Selcuk, Ahmet
In this study, Taguchi method was used to determine optimum conditions for the dissolution of ulexite in perchloric acid slutions. For optimization process; solid-to-liquid ratio, reaction time, particle size and acid concentration were chosen as parameters. In the experiment, stirring speed and reaction temperature were kept as constant. The ranges of experimental parameters-were between 0.1-0.2 g/cm(3) for solid-to-liquid ratio, 1.5-2.5 M for acid concentration, 165.0-512.5 mu m for particle size and 12-36 min for reaction time. In the end of the experimental sections the optimum conditions were determined as 0.1 g/mL for solid to liquid ratio; 215 mu m for particle size; 24 min for reaction time; 500 rpm for stirring speed; 30 degrees C for reaction temperature and 2 mol/dm(3) for acid concentration. Under these conditions, it was found that the boric acid extraction from ulexite was reached a value of 99 %.
Dissolution Kinetics and Mechanism of Pandermite in Acetic Acid Solutions
(Academic Journals, 2010) Gur, Aycan; Caglayan, Firat; Yildiz, Adnan; Selcuk, Ahmet
In this study, the dissolution kinetics and mechanism of pandermite mineral was investigated using a batch reactor employing the parameters of particle size, acid concentration, solid/liquid ratio, stirring speed and reaction temperature. From experimental data, it was determined that the conversion rate of pandermite to boric acid was increased with decreasing particle size, solid/liquid ratio and increasing reaction temperature. Conversion rate increased up to 3 M, acid concentration then decreased with increasing acid concentration. It was observed that there was no important effect of stirring speed on the dissolution rate. Furthermore, it was observed that the dissolution mechanism was dependent on acid concentration due to restriction of dissolution in acetic acid solutions. The dissolution rate of pandermite mineral in acetic acid solution was examined according to homogeneous and heterogeneous chemical reaction model. It was determined from graphical and statistical methods that the reaction kinetics fitted to model in the form of first order pseudo homogeneous model [- ln (1 - X)] = kt and activation energy for the dissolution process was found to be 28.496 kj/mol. A mathematical model, which indicated the dissolution process was established.
Effective Removal of Dyes From Aqueous Systems by Waste-Derived Carbon Adsorbent: Physicochemical Characterization and Adsorption Studies
(Nature Portfolio, 2025) Kuyucu, Ali Ender; Selcuk, Ahmet; Onal, Yunus; Alacabey, Ihsan; Erol, Kadir
Due to their cost-effectiveness and high surface area, activated carbons are commonly used for the adsorption of dyes from aqueous solutions. In this study, activated carbon was synthesized from walnut shell waste via KOH activation (1:3 ratio), yielding a surface area of 2347.4 m(2)/g. Reactive Blue 19 and Reactive Red 195 adsorption behavior were studied under varying experimental conditions. These included natural pH values (6.8-7.2), dye concentrations between 50 and 1250 mg L--(1), and adsorbent dosages ranging from 0.1 to 1.0 g. Adsorption equilibrium was achieved within 150 min. The maximum adsorption capacities were found to be 1227.17 mg g(-)(1) for RB 19 and 235.74 mg g(-)(1) for RR 195. Isotherm modeling was conducted using Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models, with Freundlich providing the best fit for both dyes, indicating multilayer adsorption on heterogeneous surfaces. Thermodynamic analysis revealed that the adsorption processes were spontaneous and endothermic, with negative Gibbs free energy (Delta G degrees), positive enthalpy (Delta H degrees), and positive entropy (Delta S degrees) values. These results highlight the high adsorption performance and practical potential of walnut shell-derived activated carbon for dye removal from wastewater.
Investigation of Isothermal Parameters of Dye Adsorption Onto Active Carbon
(Health & Environment Assoc, 2015) Selcuk, Ahmet; Kuyucu, Ali Ender; Kul, Ali Riza; Onal, Gulen
The fact that active carbon adsorps colourants and heavy metals has been known for a long time and thus it is used as adsorbant in removal of such pollutants. In this study, the capacity of active carbon in removal of colourant was investigated. As active carbon, Zivzik pomegranate from Siirt district of TURKEY was used and removal of colourants of Methylene Blue and Crystal Violet was studied. Active carbon was prepared with ZnCl2 by chemical activation. BET surface area, total surface volume and surface area of active carbon were measured by hte istrument called BET. In our study, adsorptions Methylene Blue and Crystal Violet colourants to active carbon at 45 degrees C were evaluated for four different initial colourant concentrations of 200, 400, 600 and 800 mg/L graphically.